This is a problem of floating point numbers in general.

You can try to circumvent it (with some performance penalty) by using bignum.

$ perl -Mbignum -wle 'print 3.624920464501920123E+08 - 3.6249204645040
+15567E+08'
-0.0002095444
$ perl  -wle 'print 3.624920464501920123E+08 - 3.624920464504015567E+0
+8'
-0.000209510326385498
[download]

Actually I haven't checked which is more accurate, but you can give it a try.